In communication and information technology, terminals, that is to say by way of example cordless telephones, mobile radios, computers, PDAs etc., are frequently operated in a mobile form, and are operated by means of a radio link to a base station, a so-called access point. In order to enlarge the geographical field of use of a mobile terminal such as this, and in order to increase the amount of data or information which can be transmitted at the same time (bandwidth), a plurality of base stations are frequently used at the same time, with one mobile terminal being operated alternately between them. Arrangements such as these are frequently referred to as multicell mobile radio systems and are known in the form of DECT systems for cordless telephones, GSM networks for mobile radios (cellular telephones) and, for example, in the form of WLAN networks for data communication. Conventional multicell mobile radio systems in this case have the common feature that the individual radio cells, that is to say the areas in which the individual base stations can be received, overlap one another, so that a mobile terminal can be moved through the multicell mobile radio system, with a connection being able to be handed over from one base station to another base station in an overlap area between two radio cells. Particularly in geographically small radio networks, it is possible in this case to even be able to receive all of the base stations at some or all locations.
When designing a multicell mobile radio system, care must be taken to ensure that at least one of the base stations can be received with an adequate reception field strength at every location at which a mobile terminal may be intended to operate. Ideally (free-field), it is possible in this case to assume that the reception field strength is distributed radially symmetrically around a base station, so that base stations are often arranged approximately in a square grid on an area to be supplied, so that each base station covers a radio cell with a hexagonal outline, at whose center it is arranged.
In practice, the propagation of radio waves is frequently adversely affected by buildings, the landscape and other elements. Furthermore, the radio base stations do not all have the same transmission power, and do not emit the radio waves radially symmetrically, either. For this reason, radio networks are frequently designed on the basis of rough approximations and on the basis of “provisional” empirical values, and are then “surveyed”, that is to say the available reception field strength is recorded by means of a measurement receiver at a multiplicity of measurement points, in order to use these measurement results to successively optimize the radio network. Such recording of the radio coverage is in this case associated with a large amount of often manual effort and, furthermore, must be repeated whenever the radio network itself is changed or an influencing factor (for example local buildings) changes.
Attempts are frequently made to reduce the effects of these disadvantages by “overdesigning” radio networks, that is to say, for example, by choosing the transmission power of the radio base stations to be higher than necessary, or by using an unnecessarily large number of base stations. This is, of course, associated with greater costs and with greater emission of radio-frequency electromagnetic waves.
The data relating to the recorded radio coverage is used not only to ensure area coverage of a radio network but also to find the position of mobile terminals. In the simplest case, the mobile terminal is in this case interrogated via the radio network for the identification numbers of all the base stations which can be received at the present time at its location. In this case, the location of the mobile terminal is emitted as an area which corresponds to the intersection area of all the radio areas (reception areas) of the identified base stations. The position-finding accuracy therefore decreases as the size of the reception areas of the base stations increases.
In the document DE 10 2004 010 182 B3, the stationary base stations in a radio network are used to record the radio coverage. This saves manual measurements and ensures adequate radio coverage in many cases. However, the method provides only a small amount of information about the radio field strengths between the base stations.
In known multicell mobile radio systems, it has disadvantageously been found that the radio coverage must be recorded frequently and precisely for reliable operation, and such recording is associated with a large amount of effort.